http://www.shroomery.org/forums/showflat.php/Cat/0/Number/6787354
"Soap isn't toxic to mushroom mycelium, especially oysters. In addition, it has a high pH, not low, so it helps ward of contaminants. Soap is also a wetting agent. The straw used for these oysters below was soaked in soapy water for two hours just before pasteurization. Does it look like it hurt?"
I think I will try this with recycled magazines and newspapers.